1. Field of the Invention
The present invention relates to a magnetic head suspension for supporting a magnetic head slider that reads and/or writes data from and to a recording medium such as a hard disk device.
2. Related Art
In recent years, data storage devices for reading and/or writing data from and to recording mediums through a magnetic head slider have been widely used in mobile apparatuses such as notebook-type personal computers and portable music players and, along therewith, these data storage devices have been required to have high impact resistance.
For example, when a data storage device in which a pair of suspensions supporting magnetic head sliders are respectively positioned on an upper side and a lower side of a hard disk is dropped on a floor surface, the date storage device is subjected to an impulsive force.
When acceleration of the impulsive force is equal to or greater than a certain value, the magnetic head slider positioned on the lower side of the disk jumps away from the disk, and then swings back toward a disk surface of the disk to clash with the disk surface, resulting in damage of the disk surface. Accordingly, in order to increase the impact resistance of the data storage device, there is a need for enhancing impact resistance against jumping motion of the magnetic head slider so that acceleration of an impulsive force which triggers the jumping motion of the magnetic head slider is raised (that is, so that the jump motion of the magnetic head slider is prevented even if the impulsive force with greater acceleration is applied).
By the way, when the data storage device is dropped on the floor surface, the magnetic head slider positioned on the upper side of the disk is subjected to an impulsive force causing the slider to move in a direction close to the disk surface. However, an air film between the slider and the disk surface functions as buffer member, thereby effectively preventing the slider from clashing with the disk surface.
For example, by increasing load which presses the magnetic head slider toward the disk surface, it is possible to enhance impact resistance against jumping motion of the magnetic head slider.
However, it is necessary to set the load within a proper range, in order to control the height of the magnetic head slider above the disk surface. Accordingly, there is naturally a limit to the method in which the load is increased for suppressing the jumping motion of the magnetic head slider.
As another structure for suppressing the jumping motion of the magnetic head slider, there is also known a structure in which a mass of a load beam portion is reduced so that an inertia force of the load beam portion when an impulsive force is applied thereto is reduced, thus enhancing impact resistance against the jumping motion of the magnetic head slider.
However, reduction of the thickness of the load beam portion and/or formation of a hole in the load beam portion in order to reduce the mass of the load beam portion, would involve deterioration of rigidity of the load beam portion, thus inducing the problem of degradation of the vibration characteristics and the loading/unloading characteristics.
As still another structure for suppressing the jumping motion of the magnetic head slider, there has been proposed a structure in which the load beam portion supported through a load bending portion by a supporting portion such as an arm or a base plate is formed to have an extending portion extending toward the base-end side of the suspension (for example, see Japanese unexamined patent publication No. H9-082052, Japanese unexamined patent publication No. H11-039808, Japanese unexamined patent publication No. 2004-348804, and Japanese unexamined patent publication No. 2005-174506, which are hereinafter referred to as patent documents 1-4, respectively).
The conventional structure described in each of the patent documents 1-4 is configured so as make a mass of a portion of the load beam portion which is positioned on a base-end side in a suspension longitudinal direction from the load bending portion to be as equal as possible to a mass of a portion thereof which is positioned on a tip-end side of the suspension longitudinal direction from the load bending portion. The structure is advantageous in suppressing the jumping motion of the magnetic head slider at a time when being subjected to the external impulsive force, without degrading the rigidity of the load beam portion.
However, in the magnetic head suspensions described in each of the patent documents, the load beam portion is connected to a free end portion of the load bending portion, which is supported by the supporting portion in a cantilever manner. With the structure, the supporting point of the load beam portion (namely, the portion of the load beam portion which is connected to the load bending portion) may vary in the direction orthogonal to the disk surface when an impulsive force is applied thereto.
Accordingly, the magnetic head suspensions described in each of the patent documents can not sufficiently enhance impact resistance against the jumping motion of the magnetic head slider, although the problem of degradation of the rigidity of the load beam portion does not occur.
In the structure in which the load beam portion is provided with the extending portion, there has been proposed a structure in which the supporting portion is provided with a pair of supporting pieces at its tip end, the extending portion of the load beam portion is positioned within a concave portion which is defined by the pair of supporting pieces, and a balance mass member is mounted on the extending portion (see, for example, patent document 1).
Although the conventional structure is advantageous in that the mass of the tip-end side and the mass of the base-end side of the load beam portion could be effectively balanced to each other by the balance mass member, it has, on the other hand, a following problem. Specifically, the pair of supporting pieces are formed to be substantially parallel to a longitudinal center line of the magnetic head suspension so that the inertia force of the pair of supporting pieces around the longitudinal center line is increased, resulting in a problem of making it difficult to enhance resonance frequency in torsion secondary mode and torsion tertiary mode.
Furthermore, in the conventional structure, the pair of supporting pieces respectively support proximal end portions of a pair of leaf springs functioning as the load bending portion in a cantilever manner, and a proximal end portion of the load beam is connected to distal end portions of the pair of leaf springs.
That is, in the conventional structure disclosed in patent document 1, the pair of supporting pieces support the load beam portion in a cantilever manner through the pair of leaf springs. In the conventional structure, it is needed to increase width and/or thickness of the pair of supporting pieces in order to ensure rigidity of the pair of supporting pieces.
However, increase of width and/or thickness of the pair of supporting pieces involves increased mass of the distal end portion of the supporting portion, resulting in a problem that the distal end portion of the supporting portion is easy to be displaced in a direction close to the disk surface when being subjected to an impulsive force that causes the magnetic head slider to move in a direction close to the disk surface. Specifically, increase of width and/or thickness of the pair of supporting pieces results in reduction of acceleration of impulsive force that causes the balancer mass member to clash with the disk surface (that is, clash of the balancer mass member with the disk surface by impulsive force with lowered acceleration), thereby deteriorating impact resistance against the clashing motion of the balancer mass member.